The present application generally relates to the field of hydraulic power systems. In particular, the present application pertains to equipment capable of gradually engaging and/or driving a hydraulic motor (e.g., soft start systems).
In general, prior art hydraulic starting systems for starting a hydraulic motor involved the use of a primary flow control valve that slowly or partially opened to regulate the initial pressure and/or fluid flow to a hydraulic motor to be driven.
One problem associated with such prior art “soft start” systems is that they are not efficient in the use of the hydraulic fluid. For example, as the primary control valve is slowly opened, the pressure and flow is generally proportionally increased until the pressure and flow supplied to the hydraulic motor to be driven is adequate to begin to drive the motor and any load that may be applied to the motor. From the time of initial engagement of any and all intermediate transmission components and the actual rotation of the motor, any fluid pressure and flow that is bypassed or leaking through the system components is not producing any work. Thus, this lost fluid pressure and flow is directly attributable to the inefficiencies of such prior art systems.
This can be a particular concern in systems with a limited pressure reserve for powering a hydraulic motor for a limited period of time (e.g., a hydraulic accumulator based pressure source for starting an engine, etc.). As the primary flow valve(s) is/are throttled from a closed position to an open position, fluid pressure and flow are lost in the time it takes the flow and pressure to achieve a level necessary to engage and/or rotate the hydraulic motor (e.g., for purposes of starting an engine). As such, the fluid is less efficiently used during the time it takes the valve to go from fully closed to fully open, ultimately resulting in less work being performed by the motor (e.g., less cranking cycles available for hydraulically starting an engine).
Another problem which exists in these prior art systems, is that the various valves (e.g, relief valves, control valves, etc.) and/or other charging components are separated such that numerous individual connections must be made between these components using additional hydraulic lines and connectors. This increases not only the cost of such a system, but also the failure rate of the system, the potential for leaks, and the introduction of contaminants, etc.
Yet another problem which exists in the prior art, is that temperature fluctuations often create performance variations in the ability of the system to properly engage and/or start a hydraulic motor to be driven. As such, consistent and effective operation of such systems can be problematic when the system is subjected to fluctuating ambient conditions.
For at least these reasons, a need exists to provide an improved hydraulic soft start system which overcomes the aforementioned problems and others.